Touch screens are known to provide a means for displaying graphics and text in electronic devices and for entering commands to control the device or to perform various other functions to carry out the operation of the device. Touch screens are now becoming increasingly popular for use as displays in mobile telephones, particularly cellular telephones having integrated personal digital assistant (PDA) or palm-held personal computer (PPC) features. The touch screens are generally designed to operate and respond to a finger touch, a stylus tap or movement on the touch screen surface. Touching or tapping a specific point on the touch screen display activates a virtual button, feature or function found or shown at that location on the touch screen display. Typical telephone features which may be operated by touching or tapping the touch screen display include entering a telephone number, for example, by tapping or touching virtual keys of a virtual keyboard shown on the display, making a call or ending a call, navigating through an address book, increasing or decreasing the listening volume, starting or ending a call, accessing speed dialing, and locking/unlocking the telephone.
Currently, mobile phones provide security against unauthorized use by requiring a user to enter a password such as a text string or a personal identification number (PIN) using a keypad on the mobile telephone. The mobile telephone is locked against use until the user enters the correct password. In order to maximize security, the mobile telephone may require the user to enter the password every time the mobile telephone is used. In practice, for the sake of convenience and ease of remembering, users often select weak passwords (e.g., passwords that are predictable, such as a birth date). The more predictable a password may be, the easier it is for an unauthorized user to determine the password. However, the more strong a password is (e.g., a longer password), the more difficult it is for an authorized user to remember the password. Existing systems for locking computing devices fail to encourage users to select strong passwords while also providing an engaging unlock experience.